KDE Neon

KDE Neon is a KDE project that provides the latest versions of KDE software on top of the latest LTS version of Ubuntu. There are two versions of KDE Neon: the User Edition that comes with the latest released versions of KDE software, and the Developer Edition based on pre-release versions. With the Developer edition you have the choice between using the stable or the unstable branch.

KaOS

Sabayon

Sabayon is a "rolling release" distribution, meaning that you install once and have your system upgraded as new versions of installed software is added to the distribution. Perhaps not the easiest distribution for users new to Linux.

Korora

PCLinuxOS

SuperX

An Indian project, SuperX is based on Ubuntu. From the project site: SuperX uses a tweaked version of KDE and is aimed towards beginners, casual users and business looking for a well supported user-friendly Linux OS.